Interchangeable shaft for electrical devices



Jan. 10, i939.

` M. J. ARVIN INTERCHANGEABLE SHAFT FOR ELECTRICAL DEVICES Filed Oct. 7,1937 INVENTOR ATTORNEY Patented Jan. 10, 1939 UNITED STATES PATENTOFFICE INTER-CHANGEABLE SHAFT FOR ELECTRI- CAL DEVICES ApplicationOctober 7, 1937, Serial No. 167,716

6 Claims.

This invention relates to control shafts for electrical devices such asvariable resistances for use in radio sets.

An object of the invention is to improve the 5 arrangement of suchshafts and particularly to render said shafts replaceable orinterchangeable.

Other objects of the invention will be apparent from the followingdescription and accompanying drawing taken in connection with theappended claims.

The invention comprises the features of construction, combination ofelements, arrangement of parts, and methods of manufacture and operationreferred to above or which will be brought out and exemplified in thedisclosure hereinafter set forth, including the illustrations in thedrawing.

In the drawing:

Figure 1 is a side view of a replaceable control shaft according to theinvention;

Figure 2 is a sectional View of a variable resistance device adapted toreceive said shaft;

Figure 3 shows the shaft and resistance device assembled and providedwith an actuating knob;

Figure 4 is asection on the line 4-4 of Figure 3; and

Figure 5 shows the end of a modified form of shaft.

'I'he radio receiving sets manufactured today vary in their partsrequirements. For instance, one set will require a variable resistancedevice of one resistance value and terminal arrangement while anotherset has very different requirements. Likewise many different lengths ofcontrol shafts 35 are required and these also vary in constructionaccording to the kind of knob attachment desired. One shaft may bedesired with a round end and another with a fiat end and so forth. Thereare at least ten kinds of variable resisters needed to fulfill all therequirements and each type must be furnished with perhaps ten varietiesof shafts.

Heretofore the shafts have been made an integral part of the resistancedevice and hence, to meet all the needs of manufacturers and radioservice men about one hundred different models had to be carried instock.

I have invented an interchangeable shaft arrangement whereby any desiredshaft may be attached to any type of variable resistance. This makes itpossible to meet all requirements by carrying in stock only about tenkinds of shafts and ten kinds of resistance devices.

While a preferred embodiment of the invention is described herein, it iscontemplated that c'onsiderable variation may be made in the method ofprocedure and the construction of parts without departing from thespirit of the invention. In the following description and in the claims,parts will be identified by specific names for convenience, but they areintended to be as generic in their application to similar parts as theart will permit.

Referring to the drawing, the preferred shaft I comprises a cylindricalpiece of metal with parts cut away at one end to leave a flat tongue IIhaving a pair of notches I2 in opposite edges. The knob end of the shaftmay be formed in any desired Way to accommodate a knob 23, for instanceby providing a flat face I3 against which a set screw may bear.

The resistance device may comprise a case I4 containing an arcuateresistance element I and a rotatable contact arm I6 adapted to travelaround said element in contact therewith to vary the amount ofresistance in a circuit in a well known manner. Arm I6 is suitablysecured to the inner end of a stub shaft II which extends through abushing 20 affixed in the wall of case I4.

Stub shaft Il extends just beyond the open end of bushing 20 and isprovided with an annular groove 29 around the projecting portion withinwhich a clinch ring I9 is fitted to prevent stub shaft Il from slidinginto the bushing.

The end of stub shaft I1 is slotted to a depth corresponding to tongueII on shaft I0, the slot I8 thereby extending back within the bushingfor a considerable distance. The slot I8 is of such dimension as to fitover tongue II when the two shafts are brought together. It is preferredthat the two end prongs of stub shaft Il be bent together slightly so asto provide a spring-like clamping of tongue II when it is inserted inslot I8.

The length of tongue I I, and hence the depth of slot I8, should begreater than the diameter of shafts I0 and I 'I to secure good bearingwithin the bushing and eliminate play and looseness.

Clinch ring I9 is provided in elliptical form (as shown most clearly inFigure 4) so that it Will hold stub shaft I'I in place but the longdiameter of ring I9 is suflicient to allow tongue II to be inserted inslot I 8. When the two shafts are fully assembled, as shown in Figure 3,the notches I2 in tongue II will be aligned with groove 29 in stub shaftI'I so that clinch ring I9 locks them together. It will be evident thatthe shafts could only again be separated if the ring I9 were centeredwith its long axis parallel to the tongue Il,

a most unlikely occurrence especially when the shafts are mountedhorizontally, as is usual.

If desired, of course, the ring I9 may be clinched after assembly.

Figure 5 shows a modied shaft 2li having a trifurcated tongue 25, 26, 2lWith the center prong 2E offset from the others to provide a springlikebearing area upon insertion into the slot in the stub shaft. A notch 28is provided to receive the lock ring i9.

The improved shaft arrangement is applicable to shaft controlledelectrical devices generally, such as variable resistance devices,rheostats, volume controls, potentiometers, switches, variablecondensers, and the like.

The shafts may be manually or automatically controllable, long, short,flexible, rigid and formed of metal or other'material.

The arrangement provides an interchangeable, attachable, detachableshaft assembly which, when assembled will give positive action, freefrom backlash and excessive play, and which is positively lockedtogether.

While the present invention, as to its objects and advantages, has beendescribed herein as carried out in specific embodiments thereof, it isnot desired to be limited thereby but it is intended to cover theinvention broadly Within the spirit and scope of the appended claims.

What is claimed is:

1. A control shaft coupling for adjustable electrical devices comprisinga pair of circular shaft sections of substantially the same diameterhaving interlocking portions for connecting them together end-to-end,one of said portions having a slot extending back from its end andhaving a groove extending around said slotted region, the other of saidportions comprising a tongue fitting into said slot, said tongue havingedge notches in register with said groove When said shafts are ininterlocked relation, and a clinch ring in said registering groove andnotches locking said shafts together.

2. A control shaft coupling for adjustable electrical devices comprisinga pair of circular shaft sections of substantially the same diameterhaving interlocking portions for connecting them together end-to-end,one of said portions having a slot extending back from its end andhaving a groove extending around said slotted region, the other of saidportions comprising a tongue fitting into said slot, said tongue havingedge notches register with said groove when said shafts are ininterlocked relation, and a clinch ring in said registering groove andnotches locking said shafts together, and a tubular bushing surroundingsaid slotted shaft section adjacent said clinch ring, said clinch ringcomprising a ange preventing walls of said slot to take axial movementof said slotted section into said bushing.

3. A control shaft coupling for adjustable electrical devices comprisinga pair of circular shaft sections of substantially the same diameterhaving interlocking portions for conecting them together end-to-end, oneof said portions having a a slot extending back from its end and havinga groove extending around said slotted region, the other of saidportions comprising a tongue fitting into said solt, said tongue havingedge notches in register with said groove when said shafts are ininterlocked relation, and a clinch ring in said registering groove andnotches locking said shafts together, said tongue comprising a pluralityof prongs affording spring bias against the in said coupling.

4. A control shaft coupling for adjustable electrical devices comprisinga pair of circular shaft sections of substantially the same diameterhaving interlocking portions for connecting them together end-to-end,one of said portions having a slot extending back from its end andhaving a groove extending around said slotted region, the other of saidportions comprising a tongue tting into said slot, said tongue havingedge notches in register With said groove when said shafts are ininterlocked relation, and a clinch ring in said registering groove andnotches locking said shafts together, said clinch ring being ellipticalin shape to permit coupling of said shafts. V5. A control shaft couplingfor adjustable electrical devices comprising a pair of shaft sectionshaving interlocking portions for connecting them together end to end,said portions comprising non-circular interiitting parts tting togetherto form a substantially circular joint, said interfitting parts beingcorrespondingly groved to provide a circumferential groove in saidjoint, and a clinch ring in said groove locking said sections together.

6. A control shaft coupling for adjustable electrical devices comprisinga pair of shaft sections having interlocking portions for conecting themI together end to end, said portions comp-rising non-circular interttingparts tting together to forrn a substantially circular joint, saidintertting parts being correspondingly grooved to provide acircumferential grove in said joint, and

a clinch ring in said groove locking said sections together, and atubular bushing surrounding said joint adjacent one side of said clinchring, said bushing serving to maintain said shafts properly aligned andconcealing a portion of said joint, said clinch ring providing a flangepreventing axial movement of said joint further into said bushing.

MARION J. ARVIN.

up play and backlash 4

